In SX Microcontrollers, SX/B Compiler and SX-Key Tool, johncouture wrote:

Interesting idea.  On a "wireless" system the biggest problem is power .... where does it come from (i.e. battery, solar, etc).  What if you were to run two wires (24VAC) to a bank of six valves as MARK suggests.

Then have something like a 433mHz radio receiver (about $3).  The SX decodes the radio signal and decides if the message is for it, and if it is, lights up the valve via the lessons learned from experiment #1.  

To make the logic simple, the SX would receive a signal to turn on valve 101-03  (Bank 101, valve #3).  The SX would light up the valve for one minute and then turn it off.  If a second command was received within the minute, it would reset the timer and leave the valve on for another 60 seconds.  That way you have a fail safe and you don't have to send out a continuous carrier.  

The transmitter might be a little more powerful but still within the legal limit (not sure what that is but my guess is 100mW).  This would cost probably about $50-$75 but it could control up to say 256 banks of 6 vales .... Hmmm.  The trick is the receiver would need an antenna (which would probably get mowed over or knocked over with a golf ball).  Also, golf courses are pretty big and have a lot of surrounding interference (in California, we build golf courses surrounded with houses with huge picture windows, goes to show how smart we are! ;-)

On the other hand, you might be able to get a license for a stronger transmitter (say 5W). 

The X10 protocol is a good idea but it doesn't go that far.  I have these thing throughout my house and distance that the signal has to travel is a real consideration.  However, having said that, the power line in a house has to share with many noisy devices.  The irrigation system would only have valves on it.

TO ALL:

In Jon's FC-4 design (schematic above), he uses an H11AA1 to detect the presense of the 120V power (I think that was the purpose).  Is there a similar type of chip that could connect to the 24AC line at both ends that would work something like the RS-485 protocol?  I guess I'm thinking of something like a cheap, single chip design that will allow you to place a signal on the AC line one one end and take it off on the other end.

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